The invention relates generally to medical devices and more specifically to biopsy and tissue sampling and harvesting devices and methods.
It is often desirable to remove tissue from an animal for pathological evaluation, transplantation or scientific study. For example, bone marrow is sampled to verify a diagnosis, assess the extent of disease, and evaluate the damage caused by certain cancer treatments such as high dose radiation therapy and chemotherapy. Bone marrow is also harvested for transplantation in the treatment of certain hematologic diseases and cancers related to bone marrow function. The biopsy needle is still required and is inserted into the bone marrow core tissue.
Unfortunately, extracting a core of bone marrow has always been very painful for the patient or donor. Using prior art devices and methods, the biopsy needle must be aggressively twisted, rotated and oscillated to separate the core sample from the surrounding bone marrow tissue. This is aggravated by the relatively low success rate in obtaining a satisfactory sample from a single insertion into the bone. Further, it can be difficult to retain the sample during removal of the biopsy needle from the tissue which leads to repetition of the painful procedure. The aggressive movement of the needle and the design of prior art devices often destroys the architecture of the core, which can lead to difficulties in diagnosis and the need to make additional insertions into the patient. This is further a problem because the pain associated with the procedure can be a deterrent to potential bone marrow donors who must endure repeated marrow extractions to harvest a sufficient amount of bone marrow.
U.S. Pat. No. 5,333,619 to Burgio discloses a plate for use with a typical bone marrow biopsy device, which includes a biopsy needle having a distal tapered portion. The needle of such devices is tapered to reduce the diameter of the core of tissue to be severed and to trap the severed core within the lumen. The plate of Burgio is a thin curved plate which is designed to be inserted between the inner surface of the needle and the external surface of the biopsy tissue cylinder. The device is advanced within the needle until the taper of the needle forces it to put pressure on the biopsy cylinder. At this point, the entire needle assembly is rotated and rocked to loosen the tissue sample from the surrounding tissue. According to Burgio, it is critical that the plate be thin enough to fit between the needle wall and the biopsy cylinder yet retain sufficient rigidity to withstand the procedure. The entire biopsy assembly is removed to sever the sample from the surrounding tissue. The plate is then removed from the lumen of the biopsy needle to obtain the biopsy tissue.
The device of Burgio, while an improvement over prior biopsy devices, has disadvantages. The Burgio device has an opening for receiving the sample that is about one third of the overall diameter of the plate member. This results in crushing of the tissue as the plate member is forced between it and the needle. As the plate member is forced into the smaller diameter portion of the biopsy needle, the plate member is squeezed, further crushing the sample. Moreover, Burgio is similar to prior devices because it requires rotation, rocking and removal of the needle to sever the sample from the tissue. This causes pain to the patient and further crush artifact of the sample. Secondly, the needle is removed before the tissue sample is verified. If the sample is not adequate, the biopsy needle must be reinserted at a different location.
U.S. Pat. No. 4,785,826 to Ward also discloses an inner member for insertion into the biopsy needle after tissue has been pulled into the lumen. The inner member has one or more flexible segments which bend or deflect upon reaching a shoulder or area of reduced diameter at the distal end of the cannula to capture the tissue sample. The disadvantage of this device is that the entire instrument must be removed to retrieve the tissue sample; thus, requiring the entire procedure to be repeated if a second sample is required. In addition, care must be taken not to permanently bend the flexible members during the process. Doing so will not allow the inner member to return to its original shape which would make expulsion of the sample difficult.
A need has remained for devices that can reliably sever a bone marrow sample from surrounding tissue and trap the sample without crush artifact. There is also a need for devices that minimize trauma to surrounding tissue and reduce pain and discomfort for patients.
The present invention provides devices, assemblies and methods for extraction of tissue from animals. This invention is particularly useful in the removal of bone marrow.
In accordance with one aspect of the invention, a bone marrow biopsy assembly is provided for extracting bone marrow tissue samples. The assembly includes an outer cannula or biopsy needle having a tapered distal end and an extractor including an inner cannula sized for slidable insertion into the proximal end of the outer cannula. The extractor includes a cannula and a distal working end. The distal working end has a diameter larger than the diameter of the tapered portion of the biopsy needle lumen. The working end includes a body portion adjacent the cannula and a cutting head having a cutting tip. A hinge is engaged between the body portion and the cutting tip. The hinge allows the cutting head to bend when pushed into the tapered distal end of the outer cannula allowing the cutting tip to sever the tissue sample.
In use, the extractor is inserted into the outer cannula until the cutting head contacts the tapered end of the outer cannula. Pressure is applied to the extractor causing the cutting head to bend allowing the cutting tip to sever the tissue sample. The bending of the cutting also secures the sample in the inner cannula. The outer cannula can be left in place until a good sample is verified. Subsequent extractions can be performed by adjusting the biopsy needle and inserting another extractor if additional samples are necessary.
One object of the present invention is to provide improved devices and assemblies for extracting tissue samples. A further object is to provide a device that allows the procedures of sampling and harvesting tissue to be repeated if necessary without having to make another hole in the bone cortex. These and other objects, advantages, and benefits are accomplished according to the devices, assemblies and methods of the present invention.